kpatch/0012-symbol-lookup-enhancement.patch

From cf0a8995e6924d8130087a4859c5bf619515768d Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Wed, 26 Feb 2020 22:03:55 -0500
Subject: [PATCH 12/21] symbol lookup enhancement

For symbols which have same name in one module or have
length longger than KSYM_NAME_LEN(128 bytes). we add
some work around to lookup another unique symbol and add
relative offset to get the actual symbol. This patch
depend on a kernel patch to deal with new relocation
style.

Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
---
 kmod/patch/kpatch-patch.h          |   4 +
 kpatch-build/create-diff-object.c  |  46 ++++++++++-
 kpatch-build/create-klp-module.c   |  26 ++++--
 kpatch-build/kpatch-build          |  12 +++
 kpatch-build/kpatch-intermediate.h |   2 +
 kpatch-build/lookup.c              | 123 ++++++++++++++++++++++++++++-
 kpatch-build/lookup.h              |  13 +++
 7 files changed, 217 insertions(+), 9 deletions(-)

diff --git a/kmod/patch/kpatch-patch.h b/kmod/patch/kpatch-patch.h
index da4f6a0..3530f66 100644
--- a/kmod/patch/kpatch-patch.h
+++ b/kmod/patch/kpatch-patch.h
@@ -30,6 +30,8 @@ struct kpatch_patch_func {
 	unsigned long sympos;
 	char *name;
 	char *objname;
+	char *ref_name;
+	long ref_offset;
 };
 
 struct kpatch_patch_dynrela {
@@ -41,6 +43,8 @@ struct kpatch_patch_dynrela {
 	char *objname;
 	int external;
 	long addend;
+    char *ref_name;
+    long ref_offset;
 };
 
 struct kpatch_pre_patch_callback {
diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 5f90c6b..1bec4f4 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -2748,6 +2748,28 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
 			funcs[index].old_size = result.size;
 			funcs[index].new_size = sym->sym.st_size;
 			funcs[index].sympos = result.pos;
+			if (lookup_is_duplicate_symbol(table, sym->name, objname, result.pos)) {
+				struct lookup_refsym refsym;
+				long offset;
+
+				if (lookup_ref_symbol_offset(table, sym->name, &refsym, objname, &offset))
+					ERROR("unresolvable ambiguity on symbol %s\n", sym->name);
+
+				funcs[index].ref_offset = offset;
+
+				/*
+				 * Add a relocation that will populate
+				 * the funcs[index].ref_name field.
+				 */
+				ALLOC_LINK(rela, &relasec->relas);
+				rela->sym = strsym;
+				rela->type = absolute_rela_type;
+				rela->addend = offset_of_string(&kelf->strings, refsym.name);
+				rela->offset = (unsigned int)(index * sizeof(*funcs) +
+					offsetof(struct kpatch_patch_func, ref_name));
+
+			}
+
 
 			/*
 			 * Add a relocation that will populate
@@ -2767,7 +2789,7 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
 			ALLOC_LINK(rela, &relasec->relas);
 			rela->sym = strsym;
 			rela->type = absolute_rela_type;
-			rela->addend = offset_of_string(&kelf->strings, sym->name);
+			rela->addend = offset_of_string(&kelf->strings, strndup(sym->name, KSYM_NAME_LEN-1));
 			rela->offset = (unsigned int)(index * sizeof(*funcs) +
 			               offsetof(struct kpatch_patch_func, name));
 
@@ -2886,6 +2908,7 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
 	struct lookup_result result;
 	char *sym_objname;
 	int ret, vmlinux, external;
+	long ref_offset;
 
 	vmlinux = !strcmp(objname, "vmlinux");
 
@@ -3094,12 +3117,28 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
 			log_debug("lookup for %s @ 0x%016lx len %lu\n",
 			          rela->sym->name, result.value, result.size);
 
+			ref_offset = 0;
 			/* Fill in ksyms[index] */
 			if (vmlinux)
 				ksyms[index].src = result.value;
-			else
+			else {
 				/* for modules, src is discovered at runtime */
 				ksyms[index].src = 0;
+				if (lookup_is_duplicate_symbol(table, rela->sym->name, objname, result.pos)) {
+					struct lookup_refsym refsym;
+
+					if (lookup_ref_symbol_offset(table, rela->sym->name, &refsym, objname, &ref_offset))
+						ERROR("unresolvable ambiguity on symbol %s\n", rela->sym->name);
+
+					/* add rela to fill in ref_name field */
+					ALLOC_LINK(rela2, &krela_sec->rela->relas);
+					rela2->sym = strsym;
+					rela2->type = absolute_rela_type;
+					rela2->addend = offset_of_string(&kelf->strings, refsym.name);
+					rela2->offset = (unsigned int)(index * sizeof(*krelas) +
+						offsetof(struct kpatch_relocation, ref_name));
+				}
+			}
 			ksyms[index].pos = result.pos;
 			ksyms[index].type = rela->sym->type;
 			ksyms[index].bind = rela->sym->bind;
@@ -3108,7 +3147,7 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
 			ALLOC_LINK(rela2, &ksym_sec->rela->relas);
 			rela2->sym = strsym;
 			rela2->type = absolute_rela_type;
-			rela2->addend = offset_of_string(&kelf->strings, rela->sym->name);
+			rela2->addend = offset_of_string(&kelf->strings, strndup(rela->sym->name, KSYM_NAME_LEN-1));
 			rela2->offset = (unsigned int)(index * sizeof(*ksyms) + \
 					offsetof(struct kpatch_symbol, name));
 
@@ -3127,6 +3166,7 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
 			krelas[index].addend = rela->addend;
 			krelas[index].type = rela->type;
 			krelas[index].external = external;
+			krelas[index].ref_offset = ref_offset;
 
 			/* add rela to fill in krelas[index].dest field */
 			ALLOC_LINK(rela2, &krela_sec->rela->relas);
diff --git a/kpatch-build/create-klp-module.c b/kpatch-build/create-klp-module.c
index a97b146..0b441fa 100644
--- a/kpatch-build/create-klp-module.c
+++ b/kpatch-build/create-klp-module.c
@@ -38,7 +38,9 @@ enum loglevel loglevel = NORMAL;
  */
 static struct symbol *find_or_add_ksym_to_symbols(struct kpatch_elf *kelf,
 						  struct section *ksymsec,
-						  char *strings, int offset)
+						  char *strings, int offset,
+						  char *ref_name,
+						  long ref_offset)
 {
 	struct kpatch_symbol *ksyms, *ksym;
 	struct symbol *sym;
@@ -67,9 +69,14 @@ static struct symbol *find_or_add_ksym_to_symbols(struct kpatch_elf *kelf,
 
 	objname = strings + rela->addend;
 
-	snprintf(pos, 32, "%lu", ksym->pos);
 	/* .klp.sym.objname.name,pos */
-	snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, pos);
+	if (!ref_name) {
+		snprintf(pos, 32, "%lu", ksym->pos);
+		snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, pos);
+	} else {
+		snprintf(pos, 32, "%ld", ref_offset);
+		snprintf(buf, 256, KLP_SYM_PREFIX "%s-%s,%s", objname, ref_name, pos);
+	}
 
 	/* Look for an already allocated symbol */
 	list_for_each_entry(sym, &kelf->symbols, list) {
@@ -176,6 +183,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 	struct rela *rela;
 	char *objname;
 	unsigned int nr, index, offset, dest_off;
+    char *ref_name;
 
 	krelas = krelasec->data->d_buf;
 	nr = (unsigned int)(krelasec->data->d_size / sizeof(*krelas));
@@ -200,6 +208,15 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 
 		objname = strings + rela->addend;
 
+		/* Get the unique ref_name */
+		rela = find_rela_by_offset(krelasec->rela,
+					   (unsigned int)(offset + offsetof(struct kpatch_relocation, ref_name)));
+		if (!rela)
+			ref_name = NULL;
+		else {
+			ref_name = strings + rela->addend;
+		}
+
 		/* Get the .kpatch.symbol entry for the rela src */
 		rela = find_rela_by_offset(krelasec->rela,
 			(unsigned int)(offset + offsetof(struct kpatch_relocation, ksym)));
@@ -207,8 +224,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 			ERROR("find_rela_by_offset");
 
 		/* Create (or find) a klp symbol from the rela src entry */
-		sym = find_or_add_ksym_to_symbols(kelf, ksymsec, strings,
-							(unsigned int)rela->addend);
+		sym = find_or_add_ksym_to_symbols(kelf, ksymsec, strings, (unsigned int)rela->addend, ref_name, krelas[index].ref_offset);
 		if (!sym)
 			ERROR("error finding or adding ksym to symtab");
 
diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build
index 4896136..8bef7fb 100755
--- a/kpatch-build/kpatch-build
+++ b/kpatch-build/kpatch-build
@@ -1015,6 +1015,18 @@ for i in $FILES; do
 			SYMTAB="${KOBJFILE_PATH}.symtab"
 			SYMVERS_FILE="$SRCDIR/Module.symvers"
 
+			unset KCFLAGS
+			remove_patches
+			cd "$SRCDIR" || die
+			if [ -z "$USERMODBUILDDIR" ];then
+				CROSS_COMPILE="$ARCH_COMPILE" make "-j$CPUS" ${KOBJFILE} 2>&1 | logger || die
+			else
+				CROSS_COMPILE="$ARCH_COMPILE" make -C "$USERMODBUILDDIR" M="$USERMODBUILDDIR" "-j$CPUS" $USERMODFLAGS $TARGETS 2>&1 | logger || die
+			fi
+			cp ${KOBJFILE} ${KOBJFILE_PATH}
+			apply_patches
+			cd "$TEMPDIR" || die
+
 			if [ "$OOT_MODULE" == "yes" ];then
 				BUILDDIR="/lib/modules/$ARCHVERSION/build/"
 				SYMVERS_FILE="$TEMPDIR/Module.symvers"
diff --git a/kpatch-build/kpatch-intermediate.h b/kpatch-build/kpatch-intermediate.h
index 7230cd4..7247cac 100644
--- a/kpatch-build/kpatch-intermediate.h
+++ b/kpatch-build/kpatch-intermediate.h
@@ -39,6 +39,8 @@ struct kpatch_relocation {
 	long addend;
 	char *objname; /* object to which this rela applies to */
 	struct kpatch_symbol *ksym;
+    char *ref_name;
+    long ref_offset;
 };
 
 struct kpatch_arch {
diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c
index 4e2fcb9..190a7d8 100644
--- a/kpatch-build/lookup.c
+++ b/kpatch-build/lookup.c
@@ -44,6 +44,7 @@ struct object_symbol {
 	unsigned long size;
 	char *name;
 	int type, bind;
+	int sec_index;
 };
 
 struct export_symbol {
@@ -248,6 +249,7 @@ static void symtab_read(struct lookup_table *table, char *path)
 
 		table->obj_syms[i].value = value;
 		table->obj_syms[i].size = strtoul(size, NULL, 0);
+		table->obj_syms[i].sec_index = atoi(ndx);
 
 		if (!strcmp(bind, "LOCAL")) {
 			table->obj_syms[i].bind = STB_LOCAL;
@@ -398,6 +400,15 @@ int lookup_local_symbol(struct lookup_table *table, char *name,
 	for_each_obj_symbol(i, sym, table) {
 		if (sym->bind == STB_LOCAL && !strcmp(sym->name, name))
 			pos++;
+		else {
+			/* symbol name longer than KSYM_NAME_LEN will be truncated
+			 * by kernel, so we can not find it using its original
+			 * name. we need to add pos for symbols which have same
+			 * KSYM_NAME_LEN-1 long prefix.*/
+			if (strlen(name) >= KSYM_NAME_LEN-1 &&
+					!strncmp(sym->name, name, KSYM_NAME_LEN-1))
+				pos++;
+		}
 
 		if (table->local_syms == sym) {
 			in_file = 1;
@@ -429,16 +440,25 @@ int lookup_global_symbol(struct lookup_table *table, char *name,
                          struct lookup_result *result)
 {
 	struct object_symbol *sym;
+	unsigned long pos = 0;
 	int i;
 
 	memset(result, 0, sizeof(*result));
 	for_each_obj_symbol(i, sym, table) {
+		/* symbol name longer than KSYM_NAME_LEN will be truncated
+		 * by kernel, so we can not find it using its original
+		 * name. we need to add pos for symbols which have same
+		 * KSYM_NAME_LEN-1 long prefix.*/
+		if (strlen(name) >= KSYM_NAME_LEN-1 &&
+				!strncmp(sym->name, name, KSYM_NAME_LEN-1))
+			pos++;
+
 		if ((sym->bind == STB_GLOBAL || sym->bind == STB_WEAK
 			|| sym->bind == STB_GNU_UNIQUE) &&
 		    !strcmp(sym->name, name)) {
 			result->value = sym->value;
 			result->size = sym->size;
-			result->pos = 0; /* always 0 for global symbols */
+			result->pos = pos;
 			return 0;
 		}
 	}
@@ -485,6 +505,107 @@ char *lookup_exported_symbol_objname(struct lookup_table *table, char *name)
 	return NULL;
  }
 
+int lookup_is_duplicate_symbol(struct lookup_table *table, char *name,
+		char *objname, unsigned long pos)
+{
+	struct object_symbol *sym;
+	int i, count = 0;
+	char posstr[32], buf[256];
+
+	for_each_obj_symbol(i, sym, table)
+		if (!strcmp(sym->name, name)) {
+			count++;
+			if (count > 1)
+				return 1;
+		}
+
+	/* symbol name longer than KSYM_NAME_LEN will be truncated
+	 * by kernel, so we can not find it using its original
+	 * name. Here, we consider these long name symbol as duplicated
+	 * symbols. since create_klp_module will create symbol name 
+	 * format like .klp.sym.objname.symbol,pos, so we consider name
+	 * length longer than KSYM_NAME_LEN-1 bytes as duplicated symbol*/
+	snprintf(posstr, 32, "%lu", pos);
+	snprintf(buf, 256, KLP_SYM_PREFIX "%s.%s,%s", objname, name, posstr);
+	if (strlen(buf) >= KSYM_NAME_LEN-1)
+		return 1;
+
+	return 0;
+}
+
+struct object_symbol *lookup_find_symbol_by_name(struct lookup_table *table, char *name)
+{
+	struct object_symbol *sym;
+	unsigned long pos = 0;
+	int i, match = 0, in_file = 0;
+
+	if (!table->local_syms)
+		return NULL;
+
+	for_each_obj_symbol(i, sym, table) {
+		if (sym->bind == STB_LOCAL && !strcmp(sym->name, name))
+			pos++;
+
+		if (table->local_syms == sym) {
+			in_file = 1;
+			continue;
+		}
+
+		if (!in_file)
+			continue;
+
+		if (sym->type == STT_FILE)
+			break;
+
+		if (sym->bind == STB_LOCAL && !strcmp(sym->name, name)) {
+			match = 1;
+			break;
+		}
+	}
+
+	if (!match) {
+		for_each_obj_symbol(i, sym, table) {
+			if ((sym->bind == STB_GLOBAL || sym->bind == STB_WEAK) &&
+					!strcmp(sym->name, name)) {
+				return sym;
+			}
+		}
+		return NULL;
+	}
+
+	return sym;
+}
+
+int lookup_ref_symbol_offset(struct lookup_table *table, char *name,
+		struct lookup_refsym *refsym,
+		char *objname, long *offset)
+{
+	struct object_symbol *orig_sym, *sym;
+	int i;
+
+	orig_sym = lookup_find_symbol_by_name(table, name);
+	if (!orig_sym)
+		ERROR("lookup_ref_symbol_offset");
+	memset(refsym, 0, sizeof(*refsym));
+
+	/*find a unique symbol in the same section first*/
+	for_each_obj_symbol(i, sym, table) {
+		if (!strcmp(sym->name, name) || sym->type == STT_FILE ||
+				sym->sec_index != orig_sym->sec_index ||
+				strchr(sym->name, '.'))
+			continue;
+
+		if (!lookup_is_duplicate_symbol(table, sym->name, objname, 1)) {
+			refsym->name = sym->name;
+			refsym->value = sym->value;
+			*offset = (long)orig_sym->value - (long)sym->value;
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
 #if 0 /* for local testing */
 static void find_this(struct lookup_table *table, char *sym, char *hint)
 {
diff --git a/kpatch-build/lookup.h b/kpatch-build/lookup.h
index 420d0f0..fed3fe9 100644
--- a/kpatch-build/lookup.h
+++ b/kpatch-build/lookup.h
@@ -1,6 +1,9 @@
 #ifndef _LOOKUP_H_
 #define _LOOKUP_H_
 
+#include "kpatch-elf.h"
+#define KSYM_NAME_LEN 128
+
 struct lookup_table;
 
 struct lookup_result {
@@ -14,6 +17,11 @@ struct sym_compare_type {
 	int type;
 };
 
+struct lookup_refsym {
+	char *name;
+	unsigned long value;
+};
+
 struct lookup_table *lookup_open(char *symtab_path, char *symvers_path,
 				 char *hint, struct sym_compare_type *locals);
 void lookup_close(struct lookup_table *table);
@@ -23,5 +31,10 @@ int lookup_global_symbol(struct lookup_table *table, char *name,
                          struct lookup_result *result);
 int lookup_is_exported_symbol(struct lookup_table *table, char *name);
 char *lookup_exported_symbol_objname(struct lookup_table *table, char *name);
+int lookup_is_duplicate_symbol(struct lookup_table *table, char *name,
+		char *objname, unsigned long pos);
+int lookup_ref_symbol_offset(struct lookup_table *table, char *name,
+                         struct lookup_refsym *refsym, char *objname,
+			 long *offset);
 
 #endif /* _LOOKUP_H_ */
-- 
2.18.1